1. Technical Field
The present invention relates to slide rails for use in a drawer and a paper tray of an apparatus such as a copier, a facsimile machine, or a printer, and further relates to a sheet feed device incorporating the slide rails and paper tray and an image forming apparatus including the sheet feed device.
2. Related Art
Conventionally, slide rails have been configured such that a retainer with a rotary member is assembled between an outer rail and an inner rail. The retainer with a rotary member mounted in the slide rail includes plural ball bearings and the retainer to hold the plural ball bearings so as to be rotatable. The slide rail of the type in which the retainer with a rotary member is mounted between the outer rail and the inner rail is configured such that the inner rail slides relative to the outer rail and the ball bearings in the retainer with a rotary member rotate. Accordingly, the slide rails slidably moves smoothly (see, for example, JP-2000-287771-A, JP-2001-204564-A, and JP-2010-120554-A).
However, the slide rail as disclosed in the above publications required much time to assemble.
As an approach to solve the above problem, a slide rail without a retainer with a rotary member has been proposed (see, for example, JP-2001-173305-A). As illustrated in FIG. 14, a conventional slide rail 101 disclosed in the JP-2001-173305-A includes an outer rail 110; an inner rail 120; a large diameter roller 103; and a pair of small diameter rollers 104. The inner rail 120 is combined with the outer rail 110 so as to be pushed in and pulled out from the outer rail 110. The large diameter roller 103 is mounted at a distal end in the pushing-in direction of the inner rail 120 so as to engage between both inner rims 111 of the outer rail 110. The pair of small rollers 104 is mounted at a proximal end in the pulling-out direction of the outer rail 110 so as to sandwich an inner rim 121 of the inner rail 120. The large diameter roller 103 is mounted to a pinhole 120a formed on the inner rail 120 with a pin bearing 122. The small diameter roller 104 is mounted to a pinhole 110a formed on the outer rail 110 with a pin bearing 112.
In the conventional art, because the slide rail 101 includes two rails of the outer rail 110 and the inner rail 120, the inner rail 120 ought to slide over the entire length of the outer rail 110. The longer the sliding length of the inner rail 120 is, the longer the entire length of the outer rail 110. As the sliding amount of the inner rail 120 with respect to the outer rail 110 increases, the distance between the small diameter roller 104 serving as a support roller and a leading end of the inner rail 120 in the pulling-out direction also increases. Accordingly, when the inner rail 120 is moved in the pulling-out direction from the outer rail 110, a load exerted on the leading end of the inner rail 120 increases and the inner rail 120 is damaged. Without reinforcing the inner rail 120, the sliding distance of the inner rail 120 is limited.
To cope with the problem, two inner rails 120 can be mounted inside the outer rail 110 such that inner sides of the inner rails 120 face each other to reinforce the inner rail 120. However, the thickness of the slide rail 101 is increased, thereby enlarging the slide rail 101. Therefore, securing the strength of the slide rail 101 without making the slide rail 101 larger has been difficult.